Long Term Drought Signature of Standardized Vegetation Index

Abstract

Increasing climate variability as a result of anthropogenic climate change has brought about greater occurrences of extreme weather events and conditions. A topic of great interest is how climate variability and weather extremes will af- fect the hydrological budget on regional and global scales. In the present study, radiometric re ectance of vegetation measured by spectral sensors on MODIS- Aqua and Terra satellites is used to evaluate vegetation stress as an indication of drought. The objective of this study is to evaluate trends in drought frequency, extent and severity over the last 15 years based on remotely sensed data. This is achieved by plotting the deviation of Normalized Di erence Vegetation In- dex (NDVI) values from location speci ed average NDVI values. NDVI values since 2000 are standardized by location and time of year during the height of the plants growing season. In addition to plotting a time series of growing season vegetation condition, the study aims to compare Normalized Di erence Vegetation Indexs temporal and spatial drought signature to that of estab- lished hydrological methods of de ning and measuring drought, primarily the United States Drought Monitor. The deviation of NDVI values from standard- ized NDVI average values are overlapped with University of Nebraskas Drought Monitors assessment of drought conditions over the continental United States from the respective temporal and spatial setting.